Ring oscillators are popular in applications such as voltage controlled oscillators (VCOs), clock generation in microprocessor, carrier synthesis in cellular phones, phase-locked loops, and data and clock recovery circuits. A ring oscillator is denoted as a free-running oscillator in that no timing signal or control signal is used to initiate the oscillation. Ring-oscillator-implemented VCOs and related free-running oscillator components are among the most power-hungry components in any electronic system. Thus low-power VCO design poses fundamental challenges.
Accordingly, there is a need in the art for improved low-power VCO designs.